Though obvious to many, Casey Affleck now admits his film 'I'm Still Here' is more mockumentary than documentary.

Speaking to the New York Times, the director says Joaquin Phoenix gives "a terrific performance, it's the performance of his career."

According to the report, practically none of the film is real, including candid family moments showing Phoenix as a child on the beach. Instead, actors were used.

Billed as "a documentary on Joaquin Phoenix's transition from the acting world to a career as an aspiring rapper," promotion for the film included a delirious interview with David Letterman -- who was not in on the joke.

Even so, Affleck implies that any confusion is unintentional. "I never intended to trick anybody," Casey told the NY Times. "The idea of a quote, hoax, unquote, never entered my mind."